The present invention relates to a device for coupling and decoupling optical signals which includes an optical amplifier and two optical couplers, one coupler of which is located upstream of the amplifier, and the other, downstream of the amplifier, in each of two respective transmission channels.
An optical light wave guide-transmission line for telecommunications signals is described in European Patent application EP 0 440 276. This optical light waveguide-transmission line has an amplifier and two couplers provided on opposite sides of the amplifier, which couple and decouple service signals which have other wavelengths than the telecommunications signals. The telecommunications signals, but not the service signals, are conducted through the amplifier.
It is common in a so-called add/drop multiplexer to provide two optical amplifiers in series close to each other with two couplers between them separated from each other by a filter. The first coupler thus acts to decouple the signals of one transmission channel and the second coupler acts to couple in signals from another transmission channel, which can have the same or a different wavelength from the first transmission channel. The filter connected between them has a blocking action for signals coupled out from the first coupler.